It's the elusive formula that countless fitness fans have failed to hit upon over the years.
Now a study of cyclists by scientists at Stirling University has uncovered the secret of the perfect training regime following a 29-week study.
Health and exercise scientists from the University for Sporting Excellence found that those who combine low-intensity workouts with higher pressure bouts of exercise make better progress.
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Dr Stuart Galloway, who led the study, said: "Quantity and quality of training has provided a quandary for coaches and athletes for many years."
Split into two groups, six cyclists completed a block of 80% low and 20% high-intensity training while the second group pedalled at 55% low and 45% moderate intensity.
After a four-week rest period, the groups then switched over and the results showed the block combining high and low intensity exercise sessions increased both power and performance twice as much as the block with low and moderate intensity training.
Dr Galloway added: "It is a case of training smarter. We found in these cyclists that if you can make the hard sessions harder and the easy sessions easier then you will likely see better progress. Amateur athletes tend train in a moderate intensity bracket which in our study showed much smaller improvements."